1. Field of the Invention
The present invention relates to an image display system for controlling image display in a multiple monitor environment. More specifically, it relates to an image display system for controlling image display when using a plurality of image display devices such as liquid crystal displays (LCD), CRTs, plasma displays (PDP), field emission displays (FED), digital micromirror devices (DMD), or the like which display image signals of a predetermined format used for personal computers (PC), workstations (WS) and the like.
2. Description of the Related Art
Heretofore, in PCs (or graphic cards) and image display devices, a communication system using signal lines in display signal cables, called DDC (Display Data Channel) has been used. Using this system, a PC operating system (OS) realizes a “plug and play (PnP)” function by which it can identify the optimal display frequency and resolution of an image display device automatically, and an image display system is realized in which a range of image display device adjustments, such as brightness, display position, and color, can be made remotely. Furthermore, in a communication method of an image display system using conventional DDC, remote control from a PC is only possible for an image display system connected directly to the image output terminal of a PC. This type of image display system is disclosed in Japanese Unexamined Patent Application, First Publication No. 2000-352962, and the like.
[Patent Reference 1]
Japanese Unexamined Patent Application, First Publication No. 2000-352962 (FIG. 1, paragraph 0030, lines 1 to 11).
However, in an image display system as described in Japanese Unexamined Patent Application, First Publication No. 2000-352962, if a DDC communication line connected between a PC and image display devices is shared in a multiple monitor environment using indexes, since all image display devices respond to communication at the same time, communication failures such as bus collisions occur. Thus it is difficult for the PC to identify and control the image display devices individually. Furthermore, the PC acquires and interprets information about the recommended resolutions of the image display devices and the upper display frequency limits by DDC communication with the image display devices. However, in a case where image display devices having different recommended resolutions and upper frequency limits are mixed in a multiple monitor environment using indexes, since the PC can output only one resolution and frequency at one time, it is necessary to acquire and interpret resolution and frequency information that satisfies the specifications of all of the image display devices.